In orthogonal frequency division multiplexing (OFDM), single-carrier frequency-division multiple access (SC-FDMA), Long Term Evolution (LTE), 802.16, code division multiple access (CDMA), or other wireless network technologies transmissions from different cells may share the same uplink (UL) resources. In a single cell, different data streams that belong to the same wireless transmit/receive unit (WTRU) or different WTRUs may share the same resources. Because of resource sharing, it may be desirable to adjust the WTRU's total transmission power in order to achieve a desired quality of service (QoS), acceptable intra-cell and inter-cell interference level, improved cell-edge performance, extended cell coverage, or the like. Precise power control may also be desirable in systems using multi-user multiple in/multiple out (MU-MIMO) transmissions.
Many wireless networks support open loop and closed loop power control schemes. Open loop power control may be performed to fully or partially compensate for short-term and/or long-term channel variations that are determined in the WTRU based on downlink channel estimations, channel state information, channel noise modeling, or the like. For closed loop power control, a power control command provided by a base station is signaled to the WTRU for correcting errors occurring in the open loop power control. The correction of the transmit power in the closed loop may be either accumulated or absolute.
LTE, 802.16, MIMO, or CDMA based networks may also be setup as distributed communications, systems, or networks where one or more WTRUs communicate concurrently with at least two or more base stations using multiple independent, and sometimes simultaneous, communications. Moreover, distributed communications may include relay stations (RSs). A RS, in general, is a device that relays or repeats communication back and forth between one or more WTRUs and at least one base station. In a distributed communication one or more WTRUs may simultaneously communicate with two or more relay stations and two or more base stations, as desired.
A WTRU may receive a power control command from each RS or base station it communicates with in a distributed network. This creates a problem since the power control commands are uncoordinated and sometimes conflicting with each RS or base station trying to meet it's own signal to interference plus noise ratio (SINR) level causing a less than ideal overall system performance. A need exists in distributed wireless communications for power control to reduce power consumption of a WTRU, mitigate intra-cell and inter-cell interference, and maintain a desired QoS, SINR, or block error rate (BLER).